The present invention relates to an electrode assembly for use in cathodic protection of glass-lined metallic vessels, such as water heaters.
In a known electrode for use in the cathodic protection of a glass-lined metallic vessel such as a water heater, a platinum-coated titanium wire is used as an anode. This is illustrated in FIG. 1 of the accompanying drawings, wherein the platinum-coated titanium wire 1 is held in the central aperture of a bushing 2 by a filling 3 of silicone rubber. The bushing 2 is mounted in a wall of the vessel 4. In this arrangement, the silicone rubber filling 3 deteriorates due to its immersion in cold or hot water for a long period of time, resulting in leakage of water from the vessel.
FIG. 2, illustrates another known electrode arrangement, in which the platinum-coated titanium wire 5 is held in a bushing 6 by a glass filling 7 instead of silicone rubber as in FIG. 1. The bushing 6 is threaded into a wall of the glass-lined vessel 8. An O-shaped ring 9 is inserted between the bushing 6 and the wall of the vessel 8. In this arrangement, the adhesion between the platinum-coated wire 5 and the glass filling 7 is poor, and the glass 7 is apt to break due to the differences of the thermal coefficients of expansion of the wire 5, the bushing 6 and the glass 7.
Furthermore, the conventional electrodes as shown in FIGS. 1 and 2, have the defect that the platinum-coated titanium wire has low resistance for ripple currents.
It is an object of the present invention to provide an electrode assembly for use in cathodic protection which has excellent corrosion resistance, and which can withstand alternating thermal stress for a long period of time.